Principles of knowledge-based (or expert) systems have been applied in different knowledge-rich domains such as geology, medicine, and very large scale integrated circuits (VLSI). There have been some efforts to develop expert systems for evaluation and prediction of architectural designs in this decade. This paper presents a prototype system, Energy Expert, which quickly computes the approximate yearly energy performance of a building design, analyzes the energy performance, and gives advice on possible ways of improving the design. These modifications are intended to make the building more energy efficient and help cut down on heating and cooling costs. The system is designed for the schematic design phase of an architectural project. Also discussed briefly is the reasoning behind developing such a system for the schematic design rather than the final design phase